Spinal muscular atrophy (SMA) belongs to the group of hereditary diseases affecting peripheral motor nerve - the so-called motoneuron. As a result of this disease, the muscles are weakened and, over time, muscle fibbers - the so-called muscle atrophy - are also lost. This disease does not affect the intellect. SMA is a rare disease, but it is also one of the leading causes of death in early childhood. Typical manifestations of this disease are muscular weakness with maximum involvement in the muscles of the girdles of the lower limbs. The patient has difficulty sitting or standing alone and is usually unable to walk alone. Trouble swallowing and weakened respiratory muscles are also evident in later stages of the disease. These difficulties very often lead to loss of walking ability and shortness of breath in respiratory muscle weakness, which is usually also the cause of premature death of SMA patients.
Spinal muscular atrophy type I: the most common form of disease. It is characterized by severe and rapidly worsening muscle weakness. Children are never able to sit alone. Symptoms appear soon after birth, at the latest within 6 months of life. Life expectancy without treatment is 2 years
Spinal muscular atrophy type II: is the most common moderate clinical form of the disease SMA (up to 45% of all SMA) is the so-called type II SMA, where the symptoms are already in infant and toddler age (up to 18 months of age). The patient is able to sit alone when put in a sitting position or sit up on his own, but is never able to walk independently. Patient is dependent on a mechanical or electric wheelchair. In addition to muscle weakness, there is also significant fatigue of the muscles. Over time, the patient develops tendon shortening (contractures). Patients often suffer from severe spinal scoliosis. In later stages of the disease swallowing and breathing difficulties occur, which require some form of respiratory support or artificial ventilation (UPV). Life expectancy is shortened (20-30 years)
Spinal muscular atrophy type III: the first symptom is a walking disorder due to weakening of the muscles of both lower limbs, which spread gradually to the upper limbs. Later swallowing and speaking problems are added. Symptoms are apparent after 18 months of child's life. The progression of the disease is slow and individuals usually live to maturity.
Spinal muscular atrophy type IV: manifested only in adulthood (after 30 years of life). Patients have the ability to walk independently; they show weakness in the upper or lower limbs and increased fatigue.
How did all this happen?
No one in our family had any idea about this disease. No one has ever suffered from neuromuscular disease. My mother had always paid for and underwent all the pregnancy tests and looked forward to a healthy baby.
Genetic tests have now confirmed that mum and dad are healthy carriers. My sister was also tested and is also a healthy carrier.
Anyone can take the test as a self-payer. The price of the package for the most common genetic disease costs 7000 CZK / person. There was only one single piece of information from our gynaecologist to avoid this situation. Healthcare currently does not prevent this problem by neonatal screening.
What does it mean that the disease is genetic?
Children obtain (inherit) genes from their parents. Each gene has 2 alleles (forms), one allele gets the baby from the father and the other allele of the gene from the mother. SMA is most often inherited in an autosomal recessive manner, which means that an individual in whom SMA develops must have both alleles of the SMA gene mutated is a recessive homozygote. Parents are usually carriers (heterozygotes), so they have 1 healthy allele and a second allele with mutation, the disease does not manifest themselves, but they are at risk of transferring it to their offspring. Each carrier has a 50% risk of passing on a mutant allele to its offspring. The overall probability that two healthy carriers deliver baby with SMA is 25% and is the same for all offsprings of the pair.